[113.01] Probing the Sizes of Absorbers: Correlations in the z~3.5 Lyman-alpha Forest Between Parallel Lines of Sight

G. Becker, W. L. W. Sargent (CalTech), M. Rauch (OCIW)

Studies of the intergalactic medium along parallel lines of
sight towards quasar pairs offer valuable information on the
sizes of intervening absorbers as well as provide the basis
for a test of the cosmological constant. We present a study
of two high-redshift pairs with moderate separation observed
with Keck ESI, Q1422+2309A/Q1424+2255 (z = 3.63, \theta =
39'') and Q1439-0034A/B (z = 4.25, \theta = 33''). The
crosscorrelation of transmitted flux in the Ly\alpha
forest shows a strong peak at zero velocity lag in both
pairs, suggesting that the Ly\alpha absorbers are coherent
over scales > 230-300 proper kpc. Two strong C IV systems
at z = 3.4, closely separated along the line of sight,
appear in Q1439B but not in Q1439A, consistent with the
picture of outflowing material from an intervening galaxy.
In contrast, a Mg II system at z = 1.68 does appear in both
Q1439A and B. This suggests either a single absorber of size
> 280 kpc or two separate, clustered absorbers. We
additionally examine the impact of spectral characteristics
on applying the Alcock-Paczynski test to quasar pairs,
finding a strong dependence on resolution.